Apparatus for drying battery plates



March 7, 1939. a. G. LI'NDsTRoM APPARATUS FOR DRYING BATTERY PLATES Original Filed DSC. 28, 1931 4 Sheets-Sheet 1 INVENToR k/JBRUCE G. LlNosT-Roul ATTQRNEY FIG. 4.

March 7, 1939. B. G. I INDsTRM APFARTUS FOR DRYING BATTERY PLATES 4 Sheets-Sheet.A 2

original Filed Dec. 28, '195i Q o c LI.. n

INVENTOR BRUCE G. LINDSTROM ATTORNEY March 7, 1939.-

B. G. LINDST'ROM APPARATUS FOR DRYING BATTERY PLATES `Original Filed Dec. 28, '1931-v 4 Sheetse-Sheet 3 m o mm @N N n w m NN mvENToR BRUCE- G. LmosTRoM ATTORNEY March 7, 1939. B. G LINDsTRoM 2,149,813

y APPARATUS FOR DRYING BATTERY PLATES 4 Sheets-Sheet 4 .MJU-L.

|NvENroR BRUCE G. L lNDsTR'oM Original Filed Dec. 28, 1931 ATTORNEY Patented Mar. 7, 1939 APPARATUS FOR DRYING BATTERY PLATES Bruce G. Lindstrom, Norrkoping, Sweden, assignor, by mesne assignments, to Globe-Union Inc., Milwaukee, Wis., a corporation of Delaware Original application December 28,1931, Serial No. 583,453. Divided and this application January 22, 1937, lSerial No. 121,794

` v1o Claims.

This invention relates to an oven or apparatus for drying battery plates.

The present. application is a division of my application for Method of and apparatus for drying gtry plates, iiled December 28, 1931, Serial No.

Various methods foridrying storage battery plates have been used but with the exception of drying by means of dry steam under high pressure they are generally rather slow processes requiring several hours to produce a dry plate capa.-

ble of standing up under the handling and other operations incidental to their assembly in a battery. Great difficulty has been encountered in producing a dry battery plate which is free from checks or cracks and has the proper hardness Iand other desirable qualities.

An object of the present invention is to provide an apparatus for'drying a batt'ery plate whichv carries out the operation in a rather short time, the drying period requiring from about one-half to not more than one hour and which produces a plate free from checks and cracks and with a hard surface practically free from surface dust.

' In carrying out the present invention, the

plates Ain the rst stage of thetreatment are iirstv brought up to the proper temperature for curing or setting of the paste in an atmosphere highly charged with Q02 gas.

until the chemical reactions involved in the setting or curing are completed. This second stage of the treatment is also carried out in an atmosphere highly charged with CO2 gas. Finally, after the plate material or paste is properly set, the plate is subjected to a somewhat higher temperature and consequently is dried very rapidly and this Withoutdamage done to the structure of the active material. In this nal stage, the plates are also subjected to the high temperature in an atmosphere of CO2 gas. y

' It has been found that the CO2 gas accelerates lthe drying and it is believed that it accomplishes this purpose by facilitating the releaseof mois= ture from the material vof the plates while inhibiting surface drying. It is further thought that the C02 gas combines withfthe active material of the rial of uniform structure 'in the active material of the plates. There are practically no large crystals nor the undesirable varying crystal structures present such as will be found in the paste In the second stage, this temperature is maintained Within certain limits (Cl. 34-12) I of a battery plate dried in an atmosphere free v from any Cou gas except such smallamounts as may be contained in the air. Where the crystalline structure varies, there is greater opportunity for cleavage and the material of the plates has an inherent tendency to check or crack.

An oven suitable for carrying out the method of the present invention consists essentially of a casing or housing or some equivalent structure affording a preliminary heating chamber or zone in which the plates are brought up to a setting or curing temperaturaa curing or setting chamber or zone in which the plates are maintained at the proper temperature under appropriate conditions of relative humidity to cause the paste material to set without excessive drying and a iinal l drying chamber in which the plates are dried very rapidly in an atmosphere of relatively high humidity to prevent surface drying and consequent checking of the paste material. Appro' priate conditions of temperature and humidity may be set up and maintained by providing a set of burners in the final drying blower to the setting or curing chamber or zone. Maintenance of appropriate conditions of humidity also Arequires the ,supply of predetermined amounts of fresh ai'r to the oven 'and the exhausting to the atmosphere of controlled amounts of gases and vapors from the chambers "of the oven and from the discharge duct of the fan. Obviously the particular construction or design of an oven having these essential characteristics may be widely varied and hence the embodiments illustrated in the drawings and described hereinafter should be regarded merely as a somewhat diagrammatic illustration of one type of construction.

Other objects and advantages reside in certain novel features of the construction, arrangement Figure 2 is a' plan view of the structure shown in-Flgure 1; f

-Figures 3, 4 5 and 6 are views in transverse vvertical section taken on lines 3 3, 4 4, 6-5 'and 8-8, respectively of Figure 1;

Figure 7 is a diagrammatic view showing the oven in longitudinal section; and

Figure 8 is a fragmentary view in section 111us'-' trating a .damper employed .between the delivery or discharge duct oi the fan and the final drying chamber.

Referring to the drawings, it will be seen that the oven embodying the present invention consists of an elongated casing or housing designated generally at I and which is supported above the iioor or ground level by legs or other supports 2. 'Ihe casing or housing of the oven is of double wall construction to provide structure for conveniently dening the ducts and passages hereinafter described. 'I'he plates to` be dried are carried through the oven from the left to the right as viewed in Figures 1 and 7 and for this purpose an endless conveyor designated generally at 3 may be provided. While the particular construction of the endless conveyor forms no part of the present invention and while various well known types and constructions of conveyors may be employed, the principal characteristics of the conveyor shown will be brieily and generally referred to. As shown, the conveyor 3 consists of a pair of endlesschains or iiexible elements fi, the links or sections of which are pivotally interconnected. At least certain of the links oi' each endless chain may have axles 5 mounted thereon and on which rollers or Wheels 6 are rotatably supported.

vThe rollers or wheels 6 ride on tracks 'i provided therefor, the tracks extending through the oven and also beneath the oven. The chains l are constrained to corresponding movement by means of connecting yokes 9 which are connected to the axles 5 in between the hangers or supporting brackets I@ suitably fastened to the links of the chains d and providing a means whereby the plates to be dried may be conveniently supported on the endless conveyor. The chains fi are trained about driving and idler sprockets designated at ii and i2.

In the nal drying chamber of the oven which is designated at l5, a burner I@ is provided, the burner being located in the lower portion of the chamber and servingas a source of supply of heat and CO2 gas.

The burners i6 are located in the lower part of the nal drying chamber and just above these burners inclined deector plates 8 are provided, the deector plates being interposed between the burners and the path of travel of the battery plates to be dried and being supported on cross members i9 incorporated in the oven structure.

For circulating the moist air and, COa gas through the various chambers or zones oi' the oven, a fan or blower designated at 2l is provided. The fan 2l discharges into a discharge or def livery duct or conduit 22 located above the ilnal drying chamber I 5 and dened by portions of the inner side walls'of the oven and by partitions 23 and 26, as will be understood from a coniparison of Figures 1, 6 and 7. The partition 2d which defines the lower wall oi the discharge or delivery duct is slotted as at 25 and adjacent each slot portions of the partition are bent downwardly tc provide deflectors 23. With this construction a. major portion at least of the gas delivered by the fan or blower to the discharge duct 22 flows downwardly through the slots 25 into the nal drying chamber i5. Some portion at least of the gases thus delivered to the nal drying chamberv arsenic the spaces 29 and formed between the outer and inner walls of the oven. The conduits 30 extend of vthe gases delivered thereto through the slots 25 are re-circulated, that is, they pass down between the deiiectors I8, then outwardly'between these defiectors and the baffles 21, upwardly through the final drying chamber I5, across the battery plates passing therethrough and then again downwardly through the central portion of the iinal drying chamber. The gases thus being re-circulated 'are 'continually commingling with the gases passing directly through the final drying chamber and back to the suction side of the fan. Thus, the gases which are circulated or recirculated in the final drying chamber are continually beingv refreshed.

It is to be understood that a substantial portion of the gases and vapors delivered through the slots 25 into the final drying chamber pass axially from the nal drying chamber and into other chambers or zones of the oven, and, of course, in a direction opposite to the direction of movement of the plates. In other words, the main ow of gases and vapors is axially through the oven from the right tothe left as viewed in Figures l and 7.

While portions of the gases and vapors delivered to the discharge duct 22 ow through the slots 25 and into the nal drying chamber, other portions thereof are either exhausted to the atmosphere or bypassed to the setting or curing zone of the oven. For these purposes a stack or flue 35 is provided and ,communicates with the discharge duct 22 under the control of a. damper 8b. When the damper 3b is opened, a subsmntial portion of the gases and vapors delivered to the duct 22 are vented or exhausted through the stack 3E to the atmosphere. The amount so exhausted may be cut down by appropriately adjusting the damper and of course by closing the damper 36 the escape of gases through the stack t5 may be entirely cut oi. Between the discharge duct 22 and one end oi' the curing. or setting chamber or zone 37 a bypass t@ is provided, the bypass communicating with the discharge duct under the control of a damper 39 and having ,branches M at its other end communicating with passages t2 denned between the sidewalls of the oven and communicating at their lower ends with the interior of the oven at the Setting or curing zone thereof (see Figure 4). Baines 53 may be provided adjacent the openings E in the inner walls oi' the oven, which openings aord communications betweenl the passages 2 and the setting or curing zone.

A controlled amount of fresh air may be Ysupplied to the oven by means of a motor driven fan 5d, the blast from which is directed up a lstack dl or into the opening 52 or the oven under the control of the combined damper and deflector 53. The portion oi the oven which provides the curing or setting chamber and the nal drying' chamber is preferably covered by heat insulating material designated at 5S.

In operation, the fan 2l v moves the drying medium at a fairly good velocity (from 2000 to I5000 cubic feet per minute with an oven of the capacity ci the one shown), the air moving at this velocity into the duct 22 from whence portions pass through the slots '25 to the nal drying chamber and pass the dampers 36 and 39 into the stack 35 and bypass 3B, the amount of gases traveling out through the stack 35 or through thel bypass 38, depending upon the adjustment ci the dampers36 and 39. The portion of the gas which passes into the final drying chamber is enriched by the'products of combustion and' consequently highly charged with CO2 gas and such portion of the gas is either recirculated in the final drying chamber,'advanced axially through the oven from right to left as` viewed in Figure 1 or returned to the fan 2l for recirculation. In any event, portions of the gases, rich in moisture, and CO2 gas are delivered to the inlet end of the oven and such gases serve to bring the battery plates to the desired temperature. l

By providing the ventilators or damper controlled vents ylil) at appropriate points'along the oven, a relative humidity may be maintained Withinthe desired limits. This control of humidity conditions is aided by the provision of the combined damper and deflector 53 and the fan 50.

The temperature in the preheating and curing sections is kept between 120 F. and 140 F., preferably about 125 F. The temperature in the final drying chamber is kept in the neighborhood of 350 F. It is to be understood that these temperatures are varied according to the drying time and also according to the thickness and moisture content of the battery plates to be dried. While lthe freshly pasted plate is being brought up to the desired temperature in the first drying stage,

the actual drying of the plate is retarded to a minimum by maintaining a very relatively high humidity. In the second drying stage the moisture is drawn out of the plate at a very rapid rate While still maintaining a rather high humidity around the platekwhereby to prevent surface drying with consequent checking of the material. The vapor pressure differential between the actual vapor pressure of the moisture and the theoretical Vapor pressure for the prevailing temperature should not exceed 30 millimeters of mercury or thereabout. This would correspond to a relative humidity varying from 79% at 120 F. to 91.7% at 160 F. The COz' gas not only accelerates the drying but it is thought also Acombines with the active material vof the platesY to form a lead carbonate-probably in a basic form.v

Flow of the gases axially through the oven,

i that is, from the right to the left as viewedin Figure 7, may be regulated and controlled to some extent by utilizing a slide damper 15 for at least certain of the slots 25. As illustrated in Figure 8, the damper least certain of the slots 25 to a varying degree or entirely. By blocking off certainv of these slots 25 flow of gas and vapor downwardly therethrough is prevented at the. outlet end of the Vfinal drying chamber. Asa consequence the resistance to the axial flow of the gases through the the size, shape and arrangement lof the parts may be made without departing from the spirit 'i5 may be adjusted to overlap at of the invention or the scope of` the subjoined claims.

'Ihe invention claimed is: p

1. In a drier, means forming a preliminary heating chamber, a setting or curing chamber and 'a final drying chamber, means for carrying the articles to be dried through said chambers, means in said final drying chamber for supplying heat and CO2 gas, a blower, the blower having a discharge duct leading therefrom to the final drying chamberand a return duct leading from th'enal drying chamber back io the blower, and means for bypassing gases from said discharge duct to one of the other chambers.

2. In a drier, means forming a preliminary heating chamber, a setting or curing' chamber and a final drying chamber, vmeans for carrying the articles to be vdried through said chambers,

means in said nal drying chamber -for supplying v heat and CO2 gas, a blower, the blower having a discharge duct leading therefrom to the final drying chamber, and a return duct leading from the final drying chamber back to the blower,

means for bypassing gases from said discharge means for bypassinggases from said discharge duct to one of the other chambers, and means for exhausting gases from the discharge duct.

4. In a drier, means forming a preliminary heating chamber, a setting or curing chamber and a final drying chamber, means for carrying the articles to be dried through said chambers,

means in said nal drying chamber for supplying heat and CO2 gas, a blower, the blower having a discharge duct leading `therefrom to the final drying chamber and a return duct leading fromv the final drying chamber back to the blower, means for bypassing gases from said discharge duct to one of the other chambers, and means for venting chambers of said oven to the atmosphere.

5. In a drier, means forming a preliminary heating chamber, a setting or curing chamber and a final drying chamber'r means for carrying the articles to be dried through said chambers, means in said nal drying chamber for supplying heat and CO2 gas, a blower, the blower having a discharge duct leading therefrom tothe final drying chamber and a return duct leading from the final drying chamber back to said blower, means for bypassing gases from said discharge duct to one of the other chambers, means for supplying fresh air to the final drying chamber, means fory exhausting gases from the discharge duct, and

means for venting chambers of said ovenl to the` atmosphere.

6.1 In a drier, an elongated drying oven, a burner in said oven near one end thereof, a fan having discharge and return conduits communieating with said oven in theregion of said burner whereby the products of `combustionare re-circulated through the portion of the oven adjacent said burner. a bypass leading from said discharge I conduit to a portion of the oven remote from said burner. and a damper controlled vent leading. 1`

from said discharge conduit.

7. In a drier, an elongated drying oven, a conveyor having a run extending through said oven and adapted to carry battery plates through the oven, burners adjacent one end of the oven below the path of movement of the battery plates, a fan, means coacting with the oven and fan for dening discharge, and return passages leading from the fan to and from the oven adjacent said burner whereby products'of combustion are recirculated through the portion of the oven in which the burner is located, means for conducting products of combustion from the discharge duct to a point in the oven remote from the burner, controllable means for venting the oven of products of combustion, and controllable means for supplying regulated amounts of fresh air to the oven.

8. In a drier, an elongated drying oven, a conveyor having a run extending through said oven and adapted to carry battery plates through the oven, burners adjacent one end of the oven below the path of movement of the battery plates, angled deectors interposed between the burners 'and the path of movement of the battery plates,

of products of combustion, and controllable means for supplying regulated amounts of fresh air to the oven.

9. In a drier, an elongated drying oven, an endless conveyor having a run extending through the oven for carrying battery plates therethrough, burners in the oven below the path of movement of the plates, a fan, means including a partition and a series of deectors for deiining a discharge flue leading from the fan through the deilectors to the space above the burners and a return ue leading from the space below the'- burners back to the fan, a damper controlled vent ieading from the discharge ue to the atmosphere, a damper controlled bypass leading from the discharge ue to the end portion of the oven remote from the burners, and means including a fan and a combined deiector and damper for supplying a regulated amount of fresh air to the interior of the oven.

l0. Drying apparatus comprising an oven including a humidity compartmenha drying compartment, means for maintaining the atmosphere in said humidity compartment at substantially complete saturation, a gas burner connected to said humidity compartment for heating the atmosphere therein and for supplying products of combustion to said atmosphere, means for continuously removing moisture .from the atmosphere in the drying compartment, and an endless conveyor traversing said compartments.

l BRUCE G. LINDSTROM. 

